Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only, idempotent, non-destructive behavior, so the description's real contribution is the staleness disclosure: prices are stored observations, not live checks, and each offer carries an observation timestamp. It does not say what happens for an unknown product_id or whether the similar-products list is bounded, which keeps it below the top mark.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The purpose and identifier are front-loaded, and the second sentence earns its place by flagging data staleness. The parenthetical enumeration of offer fields is dense and partly duplicates the output schema, which is the only real drag on efficiency.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter read tool with full schema coverage, an output schema, and complete annotations, the description covers purpose, selection context, and data freshness. Only edge cases (invalid or unknown product_id, size of the similar-products set) are unaddressed, and those are minor here.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both currency and product_id are already documented in detail (ISO 4217 pattern, accepted ID formats). The description only restates that lookup is by product_id and never touches the currency parameter, so it adds no meaning beyond the schema and the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Get one SkyBuyFly product by its product_id') and enumerates the payload: description, size, per-airport-shop offers, and similar products. The closing line about stored versus live prices implicitly separates it from get_live_prices and get_price_history, so an agent can place it without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete selection condition: 'Relevant when a traveller wants every airport and shop for one product,' and clarifies the tool does not check prices live. It stops short of naming the sibling to use instead for live checks or historical trends, so the routing is clear but not exhaustive.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.